#include <bits/stdc++.h>
using namespace std;
using uint = unsigned int;
using ll = long long;
using ull = unsigned long long;
using i128 = __int128;
const int N = 1e6 + 5;

void solve() {
    int a1, a2, a3;
    cin >> a1 >> a2 >> a3;
    if (a1 + 1 == a2 && a2 + 1 == a3)
        cout << "Yes" << endl;
    else
        cout << "No" << endl;
    return;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    solve();

    return 0;
}